Letter U Firearms Glossary

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Underbolts

A sliding bar, running longitudinally through the watertable of a break-open side-by-side gun's action, with openings through which the lumps of the barrels pass when the gun is closed. Under spring tension, this bar moves forward when the opening control is released and its two locking surfaces engage complementary slots (bites) in the rear of the two barrel lumps. Originally operated by a hinged tab in front of the trigger guard. Now invariably operated by a cam from Scott's [toplever] spindle. Most modern side-by-side guns lock closed in this manner.

Underhammer

A type of lock in which the hammer pivots in a vertical arc, striking the nipple on the underside of the barrel. Since the nipple's flash channel goes straight into the powder at the breech end of the barrel, ignition time is very fast. For this reason, and because it gets the hammer out of the way, underhammer locks are commonly used on muzzleloading benchrest rifles which are used for target shooting, and where accuracy is the goal.

Underlug

The locking lugs on a break-action firearm that extend from the bottom of the barrels under the chamber(s) and connect into the receiver bottom.

Underwater Firearm

A firearm specially designed for use underwater.

Upset Forging

A process that increases the diameter of a workpiece by compressing its length.


14 Other Firearms Definitions You Need To Know


SBS

Abreviation for short-barreled shotgun.

Tap, Rack, Bang

The slang term for the procedure to clear a misfeed. To clear a misfeed, tap the base of the magazine firmly to be sure it is properly seated, rack the slide to eject an empty case or feed a new round, and assess to be sure your target still needs shooting. If it does, pull the trigger to create the bang.

Ramrod

A long, slender, dowel-like tool used to force powder and shot down the bore of a muzzle-loading firearm. For hand-fired guns, normally retained in some kind of receptacle attached to the gun's barrel. Carried separately for muzzle-loading cannon.

Safety Lug

An extra flange behind the bolt handle, at the rear of a bolt action receiver (notably the Mauser Model 1898), which uses the bolt handle as an extra locking surface in the extremely unlikely event of forward bolt lug failure.

Drift

The departure of a bullet or shot charge from the normal line of flight. This can be caused by wind or the unbalanced spinning of the bullet.

WC

Abbreviation for wadcutter.

Laser Sight

A laser sight is an alternative sighting device which enables the shooter to quickly and accurately see where the firearm is aimed even when lighting or other conditions prevent using the gun's normal sights. Lasers may be located within the grips, hung from accessory rails at the front end of the gun, or placed within the firearm.

Mauser Safety

A small lever mounted to the cocking piece of a Mauser 98 action (and its copies such as the Springfield 1903), rotating on a longitudinal axis from left (Fire), up to the top (Safe, but allowing bolt movement), and over to the right (Bolt and firing pin locked Safe). While commendable for locking the firing pin instead of just the trigger, its up-and-over arc of operation requires a scope to be mounted awkwardly high. Paul Mauser is not to be blamed; when his safety was developed, telescopic sights were in such infancy as not to be worthy of mainstream consideration.

Flashbang (grenade)

A stun grenade, also known as a flash grenade, is a non-lethal explosive device used to temporarily disorient an enemy's senses. It is designed to produce a blinding flash of light and intensely loud noise "bang" of greater than 170 decibels (dB) without causing permanent injury. It was first developed by the British Army's SAS in the 1960s.
The flash produced momentarily activates all photoreceptor cells in the eye, making vision impossible for approximately five seconds, until the eye restores itself to its normal, unstimulated state. The loud blast is meant to cause temporary loss of hearing, and also disturbs the fluid in the ear, causing loss of balance.
The concussive blast of the detonation can still injure, and the heat created can ignite flammable materials such as fuel. The fires that occurred during the Iranian Embassy siege in London were caused by stun grenades.

Forcing Cone

In a shotgun barrel, A tapered area a few inches from the breech end, providing a transition between the chamber (approximately the diameter of the outside of a shotgun shell) to the bore proper (approximately the diameter of the inside of a shotgun shell). The forcing cone provides the transition between the exterior and the interior diameters of the cartridge. Older shotguns usually have more abrupt forcing cones suitable for then-current thick-walled paper shells with fibre wads. Newer shotguns usually have more gradual, longer forcing cones suitable for thinner modern plastic shells with obturating plastic shot-cup wads.

Underhammer

A type of lock in which the hammer pivots in a vertical arc, striking the nipple on the underside of the barrel. Since the nipple's flash channel goes straight into the powder at the breech end of the barrel, ignition time is very fast. For this reason, and because it gets the hammer out of the way, underhammer locks are commonly used on muzzleloading benchrest rifles which are used for target shooting, and where accuracy is the goal.

Primer

A small metal cup that contains a tiny explosive charge that is sensitive to impact. A primer is placed in the base of a shell casing to ignite the powder of the completed cartridge. It is detonated by the striking of a firing pin in the firearm.

Inertia Firing Pin

A firing pin which moves freely forward and backward in the breechblock.

Reticle

A matrix of dots, posts or lines, visible inside a rifle's telescopic sight, normally adjustable via exterior knobs for windage and elevation. After careful adjustment at a known range, the shooter aims the rifle by superimposing this matrix onto the target. With good estimation or range, cooperation from the wind, a clear eye and a steady hand, he may have a reasonable expectation of hitting his target.